Ohm Value and Reasoning on Notification Loops

[Sfrnswrth]

I need help understanding the theory behind a situation that I encountered today. We had a service order for a large warehouse installed with a Notifier AFP-200 panel with (4) NAC Extenders. We were troubleshooting the NACs on the extension that controlled the first floor. The horns and strobes were not activating during an alarm. Through troubleshooting we found that the tech before U.S. has installed 2.2k resistors at the panel, in conjunction with the EOL to come close to the 4.7k requirement. Upon removing the resistors at the panel, the horns and strobes operated properly with just the 2.2k EOL.

Here are are my questions:

1) Why did the resistors at the panel prevent the NACs from activating?
2) How does the panel still remain clear with a 2.2k EOL instead of the 4.7k?

Thanks!

Sean

 

[GrayHair]

1) The ITP resistors (In The Panel) in series caused enough voltage drop that the devices on the loop wouldn't operate.
2) SWAG here: Notifier's supervision tolerance is very wide? The supervision part of that output may be damaged?

You used resistors indicating more than one, so I'm assuming more than one NAC was involved. Did you try a 2.2K on any non-involved NACs or any inputs?

Interesting.

 

[fmtjfw]

I need help understanding the theory behind a situation that I encountered today. We had a service order for a large warehouse installed with a Notifier AFP-200 panel with (4) NAC Extenders. We were troubleshooting the NACs on the extension that controlled the first floor. The horns and strobes were not activating during an alarm. Through troubleshooting we found that the tech before U.S. has installed 2.2k resistors at the panel, in conjunction with the EOL to come close to the 4.7k requirement. Upon removing the resistors at the panel, the horns and strobes operated properly with just the 2.2k EOL.

Here are are my questions:

1) Why did the resistors at the panel prevent the NACs from activating?
2) How does the panel still remain clear with a 2.2k EOL instead of the 4.7k?

Thanks!

Sean

1) If the resistors at the panel were in series with the loop then they limited the loop current so low that the devices in parallel did not get enough current to operate.

2) Are you sure that the EOLs were supposed to be 4.7k and not 2.2k? Anyway the loop supervision circuit is probably not especially sensitive to the exact total resistance.

3) I'm guessing that the panel was checked out with resistors across the panel terminals and then loops added, and someone didn't remove the resistors when the loops were added.